The sound absorption coefficient and its influence on sound insulation

In a world where noise is omnipresent – from the constant hum of city traffic to the constant background noise in offices – the need for effective soundproofing is becoming increasingly important. A key component in the realisation of such soundproofing measures is the understanding and application of sound absorption coefficient. This value indicates the extent to which a material or surface is capable of absorbing sound waves rather than reflecting them, and therefore plays a crucial role in reducing unwanted noise.

An in-depth understanding of sound absorption coefficient is essential in order to design spaces that are not only acoustically optimised, but also contribute to improving the quality of life and work. Whether it’s designing a quiet working environment, creating a pleasant living atmosphere or acoustically planning public spaces, sound absorption coefficient is a key element to consider. In this article, we take a deeper dive into the subject and look at how sound absorption coefficient is used in the context of sound insulation to provide effective solutions against noise pollution.

Basics of the sound absorption coefficient

Definition and meaning

The sound absorption coefficient is a measure of how much sound energy is absorbed by a material or surface, as opposed to how much is reflected. It is expressed as a ratio, with a value of 1.00 (or 100%) meaning that the material absorbs all the sound that hits it, while a value of 0 represents complete reflection with no absorption. This property is particularly important in acoustics, as it is crucial for the design of rooms with controlled sound conditions. Through the targeted use of materials with a high sound absorption coefficient, the reverberation time in a room can be reduced, resulting in improved speech intelligibility and overall sound quality.

Measuring the sound absorption coefficient

The sound absorption coefficient of a material is typically determined in specialised laboratories using impedance tubes or reverberation chamber methods. These tests determine the ratio of the absorbed sound energy to the total incident sound energy on the material. The results are often presented in the form of frequency bands, as the effectiveness of a material’s sound absorption can vary at different frequencies. These detailed measurements allow designers and engineers to target acoustic materials to create optimal sound conditions for a variety of applications, from concert halls and theatres to offices and living spaces.

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The sound absorption coefficient in the context of sound insulation

Basic principles of sound insulation

Sound insulation aims to minimise the transmission of unwanted sound in order to create a pleasant and quiet environment. A key part of this is the sound absorption coefficient, which indicates how much sound energy is absorbed by a material compared to how much is reflected. A deeper understanding of these principles is crucial in order to develop effective solutions to sound insulation problems. Materials and construction techniques are specifically selected and used to optimise the sound absorption coefficient and thus contribute to sound reduction.

The role of sound absorption coefficient in noise reduction

The sound absorption coefficient of a material is a critical factor in the development of noise reduction strategies. By consciously selecting materials with high absorption coefficients, architects and designers can significantly improve indoor acoustics. In outdoor areas, certain landscaping and structural measures that have sound-absorbing properties can help reduce noise pollution from traffic, industry and other sources. The use of materials that effectively absorb sound waves can shorten reverberation time, improve sound quality and reduce overall noise levels in various environments.

Sound absorption coefficient Materials and their absorption properties

Overview of sound-absorbing materials

Choosing the right material is crucial for the effectiveness of sound absorption in various applications. Different materials have different sound absorption properties that predestine them for certain areas of application. For example, soft, porous materials such as foams and carpets are excellent at absorbing high frequencies, while heavy, dense materials such as concrete and masonry are more effective at absorbing lower frequencies.

Selecting materials for optimal sound absorption

When selecting materials for specific soundproofing requirements, it is important to consider the spectrum of sound frequencies to be absorbed. An in-depth understanding of the absorption properties of different materials enables a targeted adaptation to the acoustic needs of a room. For a room used primarily for speech transmission, materials with a high absorption rate at medium to high frequencies would be ideal. In addition, the thickness of the material plays a decisive role in the effectiveness of sound absorption. Thicker material can generally absorb a broader frequency spectrum.

Materials such as ferrite absorbers are often used in electronics to absorb electromagnetic waves, which emphasises their versatility in the application of sound and noise control measures. Other materials, such as certain types of plastics, glass and special types of quartz, can also be selected depending on their specific absorption properties and the desired area of application. The choice of the right material depends heavily on the specific requirements of the project, including the prevailing frequencies of the unwanted noise and the physical characteristics of the room.

DIN EN ISO 354 Sound absorption coefficient – A standard for measurement

DIN EN ISO 354 is an internationally recognised standard that specifies a method for measuring the sound absorption coefficient of acoustic materials. This standard is used to determine the sound absorption properties of materials used as wall or ceiling coverings or to determine equivalent sound absorption properties in a reverberation room. Its establishment makes it possible to provide a consistent and comparable basis for the evaluation of acoustic materials.

The significance of DIN EN ISO 354 extends to various areas of building and materials science. For architects, civil engineers, acousticians and material manufacturers, the standard forms an important reference point to ensure that the materials used have the required acoustic properties. By defining standardised measurement methods, the standard makes it easier to compare different materials and products in terms of their sound absorption properties.

Sound absorption is measured in accordance with DIN EN ISO 354 in a specially designed reverberation chamber. This room is designed to create a sound field condition that is as diffuse as possible. The material samples are placed in the room and the sound absorption is measured based on the changes in reverberation time before and after the samples are placed. The results obtained are then used to calculate the sound absorption coefficient of the materials, which is a measure of how much sound energy is absorbed rather than reflected by a material.

The application of this standard is far-reaching and applies not only to the selection of materials for new buildings, but also to renovation and refurbishment projects where the aim is to improve room acoustics. The sound absorption coefficient, which is measured using DIN EN ISO 354, plays a decisive role in the design of acoustically optimised rooms, whether in office buildings, educational institutions, event halls or living spaces. By providing a standardised measurement method, this standard helps to increase the quality of life and work in various environments through improved sound insulation and room acoustics.

Areas of application and case studies

Sound absorption in offices and workspaces

Improving the room acoustics in offices and workspaces is an essential measure for increasing the productivity and general well-being of employees. Noise in the office, whether from conversations, ringing telephones or keyboard noise, can lead to stress and have a negative impact on concentration and work performance. Effective sound absorption can help to minimise these disturbing noises and create a more pleasant working environment.

The role of sound absorption in increasing productivity

By using sound absorbers on ceilings, walls and even desks, reverberation in the room can be reduced and speech intelligibility improved. This is particularly important in open-plan offices, where the volume can rise quickly and the acoustics are often challenging. Materials such as acoustic sails, sound absorbers in suspended cassettes and sound-absorbing screens can be used specifically to reduce sound transmission between work areas and thus improve the acoustic quality of the room.

Design recommendations for optimum sound absorption

  • Acoustic sails and sound absorbers: These elements can be effectively attached to ceilings and walls to minimise sound reflections and thus reduce the noise level in the room. Their design flexibility allows them to be integrated as aesthetic elements that are visually appealing as well as sound-absorbing.
  • Sound-absorbing furniture and room dividers: By selecting furniture and room dividers with sound-absorbing properties, an additional layer of sound control can be achieved. These elements not only provide privacy and structure to the room, but also contribute directly to reducing noise levels.
  • Floor coverings: Carpets and special acoustic floor coverings can also contribute to sound absorption by reducing the reflection of sound waves from the floor. In combination with other measures, they reinforce the effect of sound reduction.

The challenges of sound insulation

The integration of sound insulation into architecture and interior design poses a number of challenges, especially when it comes to finding the balance between aesthetic appeal and functional efficiency. On the one hand, a room or building should be acoustically optimised to minimise noise and increase acoustic quality. On the other hand, aesthetic considerations are of central importance for the design, as they have a significant impact on people’s perception of the room.

Compromises between aesthetics and function

The challenge is to find materials and designs that fulfil both aesthetic and functional requirements. Traditional sound-absorbing materials such as acoustic panels or foams are often not visually appealing and can detract from the overall appearance of a well-designed room. Modern solutions therefore require a creative approach that incorporates innovative materials and techniques that fit seamlessly into the design concept of a space. For example, the use of specially designed sound-absorbing wall panels that are both artistic and functional can provide an effective solution. The trick is to choose materials that offer high sound absorption without compromising on aesthetic quality.

Sustainability and sound absorption materials

Another important topic is the sustainability of the sound absorption materials used. There is a growing awareness of the environmental impact of building materials, including those used for sound insulation. Bio-based and recycled materials are gaining popularity as they offer a more environmentally friendly alternative to conventional synthetic products. These materials, which are made from renewable resources or recycled materials, not only provide effective sound absorption but also help to reduce environmental impact. However, the challenge lies in ensuring that these materials are not only environmentally sustainable, but also have the required acoustic properties. Research and development plays a crucial role in identifying and improving such materials to make them viable for a wide range of applications.


Sound absorption coefficient is a critical factor in the field of sound insulation and room acoustics. It determines the extent to which materials and surfaces are able to absorb sound energy and thereby reduce the noise level and reverberation time in interior spaces. The effective use of materials with a high degree of sound absorption contributes significantly to improving the acoustic quality and general well-being in working and living areas.

In the future, sustainability aspects are expected to be increasingly integrated into the development of sound-absorbing materials. In addition, ongoing research in this area is expected to lead to new materials and technologies that will enable even more effective sound insulation solutions. Sound absorption levels therefore remain a key element in creating comfortable and productive environments, and future developments in this area promise exciting innovations for improved sound insulation and room acoustics.

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